During 1982, we will determine the serum levels of vitamin A and beta-carotene in a large group of asbestos insulation workers (approximately 2,500). All will be at least 30 years from onset of their work. These men will be at very high risk of dying of lung cancer during the next 5 years. Experience has shown that 1 in 5 deaths will be of this disease (almost 1 in 2 will be of cancer of one or another site, including many of mesothelioma). Approximately one hundred deaths of lung cancer are anticipated. Following establishment of serum levels of vitamin A and beta-carotene, these men will be kept under prospective surveillance for the next five years, to determine whether their likelihood of dying of lung cancer is related to their preexisting serum levels of the substances. Evaluation will take into account other factors, including smoking and occupational histories, and demographic and medical status.